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Process of meiosis. CSCOPE Unit 08 Lesson 02. Asexual vs. sexual reproduction. Asexual vs. sexual reproductio n. What is the advantage of an organism that reproduces sexually rather than asexually?
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Process of meiosis CSCOPE Unit 08 Lesson 02
Asexual vs. sexual reproduction • What is the advantage of an organism that reproduces sexually rather than asexually? • An organism that reproduces sexually will have more genetic diversity than one that reproduces asexually.
Meiosis i • Four Phases: • Prophase I • Metaphase I • Anaphase I (and) • Telophase I • Genetic diversity results from meiosis I.
Prophase I • Homologous (same) chromosomes pair (synapsis) • Homologous pairs called tetrads (bivalents)—two chromosome with four chromatids • Nuclear membrane dissolves • Chromosomes attach to spindle fibers and begin to move
Metaphase I • Homologous chromosomes (tetrads or bivalents) line up at the equator to form tetrads. • Random orientation results in diversity. • 50/50 chance of getting either parent’s homologue for each chromosome Tetrad
Anaphase I • Homologous chromosomes separate. • Chromosomes with TWO chromatids move to opposite poles.
Telophase I • Nuclear membrane begins to reform • Cell may quickly move to meoisis II
Meiosis II • Similar to mitosis BUT no synthesis phase (no DNA replication) • Chromatids are NOT identical because of crossing over (recombination). • Separates chromatids and produces two daughter cells with 23 chromosomes that have one chromatid each
Important Concepts!!! • Crossing Over: Exchange of genetic information between homologous chromosomes that results in recombinant chromosomes and genetic diversity
Important Concepts!!! • Independent Assortment: Chromosomes randomly line up during metaphase I, and there are various ways that the homologous chromosomes may line up—again resulting in genetic diversity.